(a) Field of the Invention
The present invention relates to a valve for pneumatic tires and, more particularly, to a valve for pneumatic tires for bicycles and automobiles.
(b) Description of the Prior Art
Known valves for pneumatic tires for bicycles and automobiles are constructed, for example, as shown in FIGS. 1 and 2 when a valve of air-pressure measuring type is shown as an example. In these figures, numeral 1 designates a stem, numeral 2 designates a plunger, numeral 3 designates a packing, numeral 4 designates a top nut, and numeral 5 designates a cap-type locking member having a slot 5a at its top. Numerals 6 and 7 respectively designate nuts, numeral 8 designates a washer, and numeral 9 designates a sealing disk made of rubber or the like. The valve constructed as above is mounted to the tire tube by matching the hole 1a, which is formed in the stem 1, to a hole formed in the tire tube and by fixing the bottom surface 9a of the sealing disk 9 to the tire tube surface by a binding agent and is fixed to the rim of the wheel by clamping the rim by the two nuts 6 and 7. To charge air to the tire tube through the abovementioned valve, the top nut 4 is loosened and air is fed from above in FIG. 1. Thus, the plunger 2 is pushed down to cause a gap between the packing 3 and inner surface of the stem 1, and air enters the tube through grooves 4a provided to the top nut 4 and through the above gap. After air is charged, the above-mentioned gap is closed as the plunger 2 is pushed up by the pressure of air in the tube. Besides, by tightening the top nut 4, the packing 3 is tightened by the flange 2c, which is formed round the plunger 2, and inner surface of the stem 1 so that air leakage from the tube is prevented. To measure the air pressure in the tube, the top nut 4 is loosened and the top end of the valve is connected to a measuring instrument. Thus, the plunger is pushed down by the measuring instrument to cause the above-mentioned gap and the air pressure in the tube is measured.
To assemble the above-mentioned valve of air pressure measuring type, the packing 3 and plunger 2 are inserted in turn into the stem 1 through its hole 1a. Then, the locking member 5 is force-fitted into the stem 1 so that the lower portion 2a of the plunger 2 passes through the slot 5a of the locking member 5 so that the plunger 2 will not rotate. After the above, the top nut 4 is screwed onto the threaded portion 2b formed at the upper portion of the plunger 2. Then, the nuts 6 and 7 are screwed onto the stem 1 and the sealing disk 9 is fixed to the stem 1 so that the valve is assembled as shown in FIG. 1.
As explained in the above, for the known valves for pneumatic tires, the number of component parts is large, assembly is not easy and, moreover, the cost of production is high because all component parts are made of metal.